however pretty sure burn percentage is controled by these cvars
z_burn_max : 0.85 : , "sv", "launcher" : Max amount for the burn effect
z_burn_rate : 0.01 : , "sv", "launcher" : How fast the burn effect grows on burning players
Also with your current method using prethink, higher tickrates will make the effect happen quicker not really gamebreaking just something to look out for when making plugins use do stuff overtime perframe, GetGameTime()
I usually use for effects over time.
Goodjob code is nice to read